## Chapter 3 Summary

• Every object in the Universe is moving relative to some other object.

• The motion of an object can be very different for people in different reference frames.

• Average speed is figured by taking the total distance that you traveled and dividing it by the total time the trip took.

• Instantaneous speed is how fast an object is going at any particular instant.

• Graphing data is a very useful way to analyze the relationships between the variables.

• The slope of the line at any one point on a position vs. time graph is the instantaneous speed of the object at that time.

• When describing the velocity of an object, the direction the object is traveling is required.

• Acceleration describes how quickly velocity changes.

• Like velocity, it is essential to provide the direction when describing acceleration.

• In physics, 'accelerating' can mean three things: speeding up, slowing down, or changing direction (turning).

• Average acceleration is figured by taking the change in the object's velocity and dividing it by the time interval.

• When air resistance is ignored, all objects near the surface of the Earth fall at the same rate regardless of their mass.

• On Earth, the free fall acceleration is 9.8 m/s/s. This is usually written as g.

• Speed – the rate at which an object's distance from a given point changes.

• Velocity – speed in a given direction.

• Graph - A visual representation of a quantitative relationship. e.g. the relationship between the distance an object travels and the time it takes for the trip.

• Acceleration – the rate at which velocity changes.

• Free fall – the motion of an object that is falling solely under the influence of gravity. i.e. there is no friction or air resistance.

• Average Speed = change in distance / change in time = Δd/Δt

• Acceleration = change in velocity / change in time = Δv/Δt

• Equations to use when object is traveling at a constant speed or velocity:

o V = Δd/Δt

• Equations to use when object is accelerating:

o a = (vf - vi)/Δt

o d = vit + 1/2at2

• meters/second (m/s) – typical unit used to describe speed or velocity

• meters/second/second (m/s/s) – typical unit used to describe acceleration

• The motion of an object can be very different for people in different reference frames.

• Average speed is figured by taking the total distance that you traveled and dividing it by the total time the trip took.

• Instantaneous speed is how fast an object is going at any particular instant.

• Graphing data is a very useful way to analyze the relationships between the variables.

• The slope of the line at any one point on a position vs. time graph is the instantaneous speed of the object at that time.

• When describing the velocity of an object, the direction the object is traveling is required.

• Acceleration describes how quickly velocity changes.

• Like velocity, it is essential to provide the direction when describing acceleration.

• In physics, 'accelerating' can mean three things: speeding up, slowing down, or changing direction (turning).

• Average acceleration is figured by taking the change in the object's velocity and dividing it by the time interval.

• When air resistance is ignored, all objects near the surface of the Earth fall at the same rate regardless of their mass.

• On Earth, the free fall acceleration is 9.8 m/s/s. This is usually written as g.

**Definitions**• Speed – the rate at which an object's distance from a given point changes.

• Velocity – speed in a given direction.

• Graph - A visual representation of a quantitative relationship. e.g. the relationship between the distance an object travels and the time it takes for the trip.

• Acceleration – the rate at which velocity changes.

• Free fall – the motion of an object that is falling solely under the influence of gravity. i.e. there is no friction or air resistance.

**Equations**• Average Speed = change in distance / change in time = Δd/Δt

• Acceleration = change in velocity / change in time = Δv/Δt

• Equations to use when object is traveling at a constant speed or velocity:

o V = Δd/Δt

• Equations to use when object is accelerating:

o a = (vf - vi)/Δt

o d = vit + 1/2at2

**Units**• meters/second (m/s) – typical unit used to describe speed or velocity

• meters/second/second (m/s/s) – typical unit used to describe acceleration